Don't force the sliderframe to 'eagerly' repaint. Allow it to be redrawn with the next Compositor pass. r=hyatt

layout/xul/base/src/nsSliderFrame.cpp

@@ -657,7 +657,7 @@ nsSliderFrame::CurrentPositionChanged(nsIPresContext* aPresContext)
     changeRect.UnionRect(thumbRect, newThumbRect);
 
     // redraw just the change
-    Invalidate(aPresContext, changeRect, PR_TRUE);
+    Invalidate(aPresContext, changeRect, PR_FALSE);
 
     if (mScrollbarListener)
       mScrollbarListener->PositionChanged(aPresContext, mCurPos, curpos);